In general, in a vehicle tire, a plurality of circumferential grooves are provided to thereby ensure drainage property of rainwater or the like at the time of running a road surface, and lateral grooves which extend in a tire width direction are provided to thereby ensure high steering property. In addition, a plurality of land blocks are defined by these circumferential grooves and lateral grooves.
In these land part blocks, at the time of tire rotation, one end part in a tire circumferential direction is present at a stepping side, and the other end part is present at a kicking-out side, the land blocks are deformed by being subjected to a resistive force from a road surface at the stepping in site; and thereafter, a ground region moves from the stepping side to the kicking-out side and then is spaced from the road surface at an end part of the kicking-out side. Subsequently, the land blocks are restored to their original shape instantaneously when it is spaced from the road surface, and at the pick-out side, the road surface is frictionally worn while being subjected to a great grounding pressure; and therefore, there occurs a so called heel and toe frictional wear that, while a vehicle runs for a long period of time, the kicking-out side is frictionally worn more greatly than at the stepping side and a step difference arises at the land block.
Here, in general, the heel and toe frictional wear significantly occurs at a site at the outside in a tire width direction of the land blocks at a shoulder portion; and therefore, conventionally, countermeasures against frictional wear of the site at the outside in the tire width direction have been mainly taken. As one of these countermeasures against frictional wear, there is a method of tilting a lateral groove angle in the tire width direction side relative to a tire circumferential direction and then restraining torsional deformation when the land blocks are grounded on a road surface. In addition, there is also known the art of forming a sipe which extends along the width direction in the land blocks and then lowering rigidity of the land blocks to thereby restrain the heel and toe frictional wear (for example, see Patent Document 1).